Such objects have been made for a long time by a two-step plastic moulding technique, where a lower part is moulded in a first mould above a plastic foil with a print prepositioned in the empty mould. Then a moulding operation is performed in the mould cavity over the lower part and the print, which faces upwards, to form a plastic moulding consisting of two halves and having a print imbedded approximately at the centre.
This known method provides products which meet all requirements as regards preservation of the quality of the print after imbedding, no formation of folds at the foil and no formation of blisters in the moulding, which is of course of a transparent, limpid plastic material, preferable acrylics.
However, this known method is relatively complicated because it requires the use of two injections moulds and transport of the half first moulded and positioning of this half and the foil in the other mould.
The Swedish Patent Specification No. 217 989 discloses a method of making injection moulded plastic objects which are provided with decorative prints. In this known method the foil provided with the print is placed at the bottom of the mould cavity, and the plastic moulding material is then introduced into the mould cavity under pressure. The foil is of such a type that it fuses with the injected plastic material without leaving visible traces, but so that the print itself remains at a distance from the mould cavity corresponding to the thickness of the foil.
In practice, however, it has been found that the foil does not fuse with the moulding material without leaving visible traces, and moreover air bubbles tend to form around the film at the underside of the object. Another point is that the method disclosed by the Swedish Patent Specification No. 217 989 can only be used for imbedding prints either at the underside or top side of the object.